1. Technical Field of the Invention
The present invention relates to liquid crystal devices which reduce wiring resistance, to manufacturing methods therefor, and to electronic apparatuses using the liquid crystal devices for display portions.
2. Description of the Related Art
As has been well known, since liquid crystal display devices have advantages in weight and electric power consumption compared to display devices using CRTs (cathode ray tubes), in particular, they are widely used for display portions of electronic apparatuses which are required to have portability.
Liquid crystal display devices generally have a structure in which two substrates are bonded to each other with a predetermined gap therebetween so that electrode forming surfaces thereof oppose each other, and liquid crystal is received in the gap; and when roughly classified in accordance with a driving mode, they can be classified into an active matrix type in which liquid crystal is driven by switching elements, and a passive matrix type in which liquid crystal is driven without using switching elements. In addition, the former, the active matrix type, can be further classified into a type which uses three-terminal elements, such as a thin-film transistor (TFT), as switching elements, and a type which uses two-terminal elements such as a thin-film diode (TFD).
The type which uses TFD elements as the switching elements among active matrix types and the simple passive matrix type have a structure in which scanning lines (common electrodes) are formed on one substrate and data lines (segment electrodes) are formed on the other substrate. Accordingly, in these types described above, since scanning signals (common signals) and data signals (segment signals) must be supplied by bonding an FPC substrate to each of the two substrates, problems of complicated bonding step and an increase in cost may arise. Accordingly, in the types described above, a technique has been proposed to bond one piece of FPC substrate to only one of the two substrates by using a structure in which all wirings or electrodes formed on the other substrate are connected to wirings formed on said one of the two substrates via conducting materials, that is, a structure is formed so that all wirings or electrodes formed on the other substrate are gathered on said one of the two substrates.
However, in the technique described above, the wirings formed on said one of the two substrates are composed of the same material as that used for transparent electrodes on said one of the two substrates, which apply a voltage to the liquid crystal. In this connection, as a material used for the transparent electrode mentioned above, ITO (Indium Tin Oxide) is generally used; however, the square resistivity of this transparent electrode material is high compared to that of a common metal. Accordingly, when the transparent electrode material described above is used for wirings for electrical connection in an area other than the display area, the resistance is naturally increased, and as a result, a problem may arise in that the image quality is adversely influenced.
In particular, recently, in order to reduce the number of connection points between a liquid crystal panel and a FPC substrate, driver ICs for driving the scanning lines (common electrodes) and the data lines (segment electrodes) are mounted on a glass substrate of the liquid crystal panel in some cases. In the case described above, various control signals and clock signals must be supplied to the driver ICs; however, when the transparent electrode material described above is used for wiring from the FPC substrate to the driver ICs, since the time constant is increased concomitant with an increase in wiring resistance, deformation of waveforms, a decrease in amplitude, and the like occur, and as a result, a problem may arise in that the operation margin is narrowed.
The present invention was made in view of the problems described above, and an object of the present invention is to provide a liquid crystal device which reduces resistance of wirings formed on a substrate, a manufacturing method therefor, and an electronic apparatus using the liquid crystal device for the display portion.